1. Field of the Invention
This invention relates to interferometric distance measuring systems. More particularly, this invention relates to interferometric distance measuring systems for measurement of a change in the distance from one point to another point, the absolute distance from one point to another point, or for control of such distances. It also relates to interferometric distance measuring systems for measurement of a change in the difference between the distances from one point to each of two other points, the difference between the absolute distances from one point to each of two other points, for control of such distance differences, or to systems for combinations of these functions.